1. Field of the Invention
The present invention relates to an electrical connector, and particularly to an electrical connector with matching differential impedance in according to high transmitting frequency and speed of signal.
2. Description of Prior Art
During the past decade, PCI standard has been a very successful, general purpose I/O interconnect standard instead of ISA standard. However, demands of emerging and future computing models will exceed the bandwidth and scalability limits that are inherent in multi-drop, parallel bus implementations. Technologies such as Central Process Unit (CPU) speeds that will exceed 10 GHz, faster memory speeds, higher-speed graphics, 1 Gigabit and 10 Gigabit Local Area Network (LAN), IEEE1394b, InfiniBand, fabrics and others will drive the need for much greater internal bandwidth. Thus, an improved industrial interconnect standard, such as 3GIO standard which is established by Intel, is required. The 3GIO architecture will be a high performance, highly flexible, scalable, reliable, stable and cost effective general purpose I/O architecture that is the natural evolution of PCI. The signaling, protocol and mechanical features of 3GIO standard is disclosed on an article entitled xe2x80x9cCreating a Third Generation I/O Interconnectxe2x80x9d, which is published on the web:
http://www.intel.com/technology/3gio/downloads/3rdGenWhitepaper.htm.
As the 3GIO standard can stand higher frequency and faster speed than the PCI and ISA, a connector conforming the 3GIO standard requires matching differential impedance as well as the insertion/return losses and the cross-talk.
In addition, impedance matching of terminals has already been discussed in U.S. Pat. Nos. 5,066,136, 5,496,183, 4,664,968 and 6,347,962. In these patents, each right angle connectors comprises a terminal module and a shielding member. The shielding member is redesigned to match the impedance of contacts of the terminal module.
An alternative electrical connector has been proposed in U.S. Pat. No. 5,713,764. A card edge connector comprises an insulative housing and a plurality of terminals received in the insulative housing. The terminals comprises body portions located in the insulative housing and contact portions for mating with corresponding terminals of a mating connector. The area of the body portion is selectively varied to vary the capacitance of the terminal, therefore, the impedance of the connector may match a given impedance of a mating electrical circuit.
However, the designs cannot be applied on an electrical connector conforming to the 3GIO standard with matching differential impedance for high frequency and fast speed. Hence, an improved electrical connector of the 3GIO standard is required to overcome the disadvantages of the conventional connector.
Accordingly, an object of the present invention is to provide an electrical connector with matching differential impedance for high frequency and speed.
In order to achieve the object set forth, an electrical connector comprises an insulative housing and a first and second terminals received in the insulative housing. The insulative housing comprises an upper wall and a lower wall defining a receiving cavity therebetween for receiving an inserted daughter card. The insulative housing defines a receiving passageway in communicating with the receiving cavity. The receiving passageway includes a first passageway section and a second passageway section. The width of the first passageway section is different from that of the second passageway section. Each of the terminals comprises a contacting portion projecting into the receiving cavity for contacting with the daughter card. The first terminal includes a resilient arm received in the receiving passageway. The width of the first terminal is smaller than that of either of the first passageway sections whereby a room in the receiving passageways is left by the terminals for tuning differential impedance.
The invention also contemplates an electrical connector comprising an insulative housing and a plurality of terminals received in the insulative housing. The insulative housing comprises an upper wall and a lower wall with a receiving cavity therebetween. The upper wall forms a plurality of rear projections at a rear end thereof and the lower wall forms a plurality of front projections at a front end thereof. Every two adjacent projections define a receiving recess. Each of the terminal comprises a mounting plate received in a corresponding receiving recess. The mounting plate forms a plurality of retention dimples for engaging with corresponding projections to securely retain the terminal in a true position.